Minor improvements in testing, builds and pipeline

[vrdmr]

Description

This PR adds the following:

1. Move from coverage to pytest-cov - moving to pytest native coverage tool.
2. Enabling --instafail to print out the stdout statements immediately.
3. Adding a description of the rules exempted in flake8.
4. Enable schedule runs every midnight for main branches in the pipeline.
5. Adding typing information in the Dispatcher's __init__() to help in static analysis - [Improvement] Adding types to function/method parameters to help with static analysis #704.
6. Minor refactoring (renaming, correct scope-levels and making static methods)

Fixes #704

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• New Unit tests were added for the changes made and CI is passing.

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[Hazhzeng]

Just curious, I don't see these packages are used anywhere in the code, are they pytest extensions and will be executed automatically?

[vrdmr]

pytest-sugar -> If you run pytest locally, this helps to present the tests better

pytest-cov -> This changes the "coverage" to use pytest-coverage - better in tracking coverages. The pipeline scripts have been updated to use this. Eg:

pytest  --instafail --cov=./azure_functions_worker --cov-report xml --cov-branch --cov-append tests/endtoend

pytest-xdist -> This can run the tests parallel, but the catch currently is that the tests rely on things from other tests (or depend on things which others are also changing at the same time, we need to improve it)

pytest-randomly -> This runs the tests randomly - exposes the ordering issues in tests, if any.

pytest-instafail -> shows failures and errors instantly instead of waiting until the end of test session, good for running when trying locally.

[vrdmr]

The pytest-sugar's output.

[Hazhzeng]

So this change will make us running the release/* branch everynight. Do you suggest moving the previous releases into releases/ancient/* branches now?

[vrdmr]

I set up the branch patterns using the best practices as recommended by AzDevops. We can change the daily runs to not target release branches.